A 150- resistor is connected in series with a 0.250-H inductor. The voltage across the resistor is

A 150- Ω resistor is connected in series with a 0.250-H inductor. The voltage across the resistor is vR = (3.80 V) cos [(720 rad/s)t].
(a) Derive an expression for the circuit current.
(b) Determine the inductive reactance of the inductor.
(c) Derive an expression for the voltage v L across the inductor.